Apparatus for producing cold cathode fluorescent lamps or the like



March 11, 1947. HERZOG APPARATUS FOR PRODUCING COLD CATHODE FLUORESCENT LAMPS OR THE LIKE 2 Sheets-Sheet 1 Original Filed March '7, 1944 c. HERZOG 2,417,361 APPARATUS FOR PRODUCING COLD CATHODE FLUORESCENT LAMPS OR THE LIKE March 11, 1947.

Original Filed March 7. 1944 2 Sheets-Sheet 2 l/VVlE/VIWR CARL HD7206 ATTORNEY I Patented Mar. 11, 1947 APPARATUS FOR PRODUCING COLD GATH- ODE FLUORESCENT LAMPS OR THE LIKE Carl Herzo g, Belleville, N. 3.

Original application March 7, 1944, Serial No. 525,446. Divided and this application June 30, 1945, Serial No. 602,570

12 Claims. R

My invention relates to apparatus, for producing electronic devices, such as gaseous discharge tubes including cold cathode fluorescent lamps, neon lamps, radio tubes or the like.

An important object of the invention is to provide apparatus of the above mentioned character for the practice of a continuous method for performing the various steps in producing the flnished product, such as a cold cathode fluorescent lamp, and will reduce the manipulation of the tube to the minimum.

A further object of the invention is to provide an apparatus of the above mentioned character for the practice of a method which will eliminate the baking of the coating of the tube in a separate furnace.

. A further object of the invention is to provide an apparatus which may be employed to evac-' uate the tube and seal in the electrode at thesame time.

A further object of the invention is to provide an apparatus which will materially reduce the cost of baking cold cathode fluorescent lamps.

A further object of the invention isto provide apparatus of the above mentioned character which will evacuate the tube through one end, and also introduce an inert gas and mercury into the tube.

A further object of the invention is to provide means for cooling the packing used to form the vacuum-tight joint.

A further object of the invention is to provide apparatus of the above mentioned character having means to connect the electrodes with the opposite pole of the source of current.

Other objects and advantages of the invention will be apparent during the course of the following description.

The present application is a division of my copending application for Method of and apparatus for making cold cathode fluorescent lamps or the like, filed March 7, 1944, Serial No. 525,446.

In the accompanying drawings forming a. part of this application, and in which like numerals are employed to designate like parts throughout the same,

Figure 1 is a central vertical longitudinal section through apparatus embodying my invention, showing the baking steps,

Figure 2 is a similar view through the tube, partly diagrammatic, showing the vacuum baking,

Figure 3 is a similar view showing sealing the bottom end of the tube,

Figure 4 is a similar view showing cutting offthe bottom end of the tube,

. the top end of-the tube and producing the finished product,

Figure 9 is an enlarged central longitudinal section through the completed lamp, Figure 10 is a perspective view, parts broken away, showing a modified manner of mounting the cathode upon the contact extension of the retainer,

Figure 11 is a similar view showing a further modified mannerof mounting the cathode upon the retainer, I

Figure 12 is a similar view showing a, further modified manner of mounting the cathode upon the retainer, and

Figure 13 isa central vertical section, upon an enlarged scale, through the tube at the point of fusing the tube to the retainer, parts broken away.

In the drawings, wherein for the purpose of iilustration is shown a preferred embodiment of my invention, the numeral l0 designates a glass tube, constituting the envelope of the cold cathode fluorescent lamp. This tube may be of any suitable diameter andlength. 'I'hese tubes are frequently a half inch in diameter and eight feet long, although the dimensions ma be varied. The inner surface of the tube In is covered or coated with a coating composition containing a finely divided luminescent or fluorescent material, and this coating is dried. I may employ the coating composition disclosed in the patent to T. M. Cortese, 2,318,060, and this coating may be applied and dried in accordance with the method disclosed in the Cortese patent. However, the coating is not baked in a separate oven, but the baking occurs as a step in my method. The tube I 0, Figure 1, has the coating composition I I, which may be the fluorescent coating composition disclosed in the Cortese patent, extending originally throughout its entire length, and dried but not baked, and this dried coating is removed from the ends of the tube ID to points l2, leaving clean or uncoated zones I3 and I 4. The tube I0 with the dried interior coating I I is vertically arranged with its opposite ends upon and held within a holder I5 to be supported thereby.

Disposed within the opposite ends of the tube II! are electrodes, including electrode shells l6.

Each electrode shell is made of the purest iron obtainable and-the interior of the shell is coated with an electron emitting material, as is well known. Each electrode shell is press fitted into a cup-shaped contact extension ll of a retainer i8, surrounding the electrode shell and spaced therefrom. The retainer l8 has alarger diameter than the electrode shell l8 and has a smaller diameter than the tube I8, and the tubeis fused tothe retainer, to provide a vacuumtight joint, as will be explained. Theretainer forms a ring or band'extending radially beyond .the electrode shell l8. If desired, the electrode shell l8 may be welded to the contact extension ii. The retainer I8 is made of a special commercial chrome-iron alloywhich has the same expansion coeiilcient as glass. The retainer l8 and lamps and to such lamps, flled January 26, 1944,

SerialNo. 519,666. 7

, I may employ the electrode shown in Figure 10. In this figure, I8 is an electrode shell, identical with the shell l8 and having a closed end II, which is welded to a wire l8. This wire is welded to the end of the contact extension II of the retainer i8. The wire l8 supports the electrode shell l8 in spaced concentric relation to the contact extension l1 and the retainer l8.-

In Figure 11, I have shown a slightly different arrangementwherein wires I9 are welded to the sides of the electrode shell l8 and to the bottom of the retainer l8. The arrangement is otherwise identical.

In Figure 12, I have shown a further similar arrangement, wherein a radial ribbon or strap 28' is welded to the end H of the electrode shell and extends outwardly beyond the same and is welded to the bottom of the retainer l8. The arrangement is otherwise identical with that shown in Figure 10.

The advantage of the electrode shown in Figures 10; 11 and 12, is that the electrode shell is spaced from the contact extension i1 and re-- tainer l8 and connected therewith by the wire or wires or ribbon and the amount oiheat which is transmitted by conduction from the shell It to the contact extension or retainer I8 is reduced. This is advantageous after the lamp has been made and is operating in use.

The electrode shell l8 corresponds to the elec,-

trode shell I8 and the same retainer and contact extension is used. I

I will now describe the operating 'units of apparatus which is used in t Practice of o k t method. The operating units are designated generally by the numerals |9 and 28. Each operating unit includes an outer block 2|, having a reduced inner end 22, which is screw threaded, and provided with a main vertical chamber 23. This main vertical chamber receives compressible packing 24, which may be rubber, asbestos, or a mixture of the same, or any other suitable ma-. terial for eiiecting a vacuum-tight joint with the glass tube ID. A follower ring 25 is movable into the chamber 23 to compress the packing 24. The

chamber 23 leads into a chamber 28. Each block is provided with a vertical opening 21 toreceive the shank 28 of a clamp or socket 29. This socket 29 may be resilient. The shank 28 is elec- 4 trically insulated upon the block 2| by an insulating sleeve 38. The shanks 28 are connected with the opposite poles of a source of current by lead wires 32, for a purpose to be described. Each reduced screw threaded extension 22 has a cap 33 mounted thereon and having screw-threaded engagement therewith, tov shift the follower rin 25 and compress the packing. This cap is provided with a water space or jacket 34, and the i0 coolant may enter at the pipe 35 and leave by the pipe 38.

The unit 20 is provided with a hot air port in,

leading into the chamber 28 and this hot air port is connected with a pipe 38, having a cut-ofl valve 39 connected therein. The pipe 38 leads to a source of hot air and the hot air is supplied through the pipe 38 so that it may enter the glass tube In at substantially 480" C. The unit 28 also has a vacuum port 48, in communication with the chamber 28 and connected with a pipe 4|, having a cut-oil valve 42 connected therein. The pipe 4| is connected with a source of vacuum.

The unit l9 has a tube 43, connected the'rewith, and this tube communicates with a port 45, leading into the chamber 28. The tube 43 has a hot air discharge tube 45 and a gas inlet tube 48, connected therewith. A rotaryvalve 41 is arranged at the union of the tubes 43, 45 and 48, and may be manipulated to place tube 43 in communication with tube 45, or tube 48 in communication with tube 48, or to cover the bore of 1 the tube 43 or tube 48.

The unit I9 is provided in its upper end with a well 48 for holding mercuryv and has a tapered recess .49 beneath the well to receive a tapered.

. rotory valve element 58. This valve element is turned by a stem 5| having a crank 52 and is urged upon its seat by a spring 53. '-The' valve.

element 58 has diametrically oppositely arranged pockets .54, for'receivlng measured amounts of the mercury anddischarging the same into an inclined port 55, leading into the chamber 28. The well 48 is in communication with avertical port 56 having a horizontal branch 5'! which leads into the recess 49 and feeds the mercury The vertical port 58'disj into the pocket 54. charges at its lower end into a horizontal recess 51', arranged beneath the valve element 58-. It is thus seen that the mercury contacts'with the upper and lower ends of the valve element-58 and seals these ends, whereby a, vacuum-tight joint is effected. x

The practice or the method is as follows I take the glass tube l8 having the dried unto baked fluorescent coating and its ends open,

and insert the same in .the holder l5, Figure l which vertically supports the tube. The electrode shells l8 are held by the sockets or clamps 29 by inserting the contact extensions I'I into these The socket 0r clamp '29 has'a'smaller diameter than the retainer l8, as clearly shown in Figure 13. The units l9 and 28 are now brought into proximity tothe oppositevends of g the tubes i8 and the electrode shells |8.-are insorted into such opposite ends. The so'ckets'29 retain the electrode shells in spaced concentric relation to the tube l8. The ends of the tube l8 are passed into the packing 24 within the chainhere 23. The units l9 and" may be supported by any suitable means. The caps 33 are now screwed up so that the follower rings 25 place the pack--v ing under compression and-form vacuum-tight ioints with the tube I8. The coolant is properly circulated through the caps33. The valve element 58 may now be in the position shown in Figure 1, whereby the inner pocket 54 is empty while the outer pocket 54 is filled with the mercury. The valve element 41 may now be in the position shown in Figure 1, whereby the port 44 is mcommunication with the hot air discharge port 45, while the port 46 is covered. The valve element 42 now covers port 40, while valve element 39 is open. Hot air is now supplied through the pipe 38 and circulates through the glass tube l and discharges from the glasstube through the pipe 45. This hot air thus supplied to the glass tube has a temperature of substantially 400 C. This hot air bakes the dried fluorescent coating I I in whole or in part. The baking treatment may continue for about half an hour. During this baking operation, any gases 'or the like liberated from the coating ll pass out with the hot air through the pipe 45. It is advantageous to bake the coating in this manner, as the tubes are long and require a large furnace for baking. The baking in accordance with my method does not plasticize the tube.

After the baking operation, Figure. 2, the valve 39 is closed and valve 4'! turned to cover port, 44, and valve 42 turned to the open position. The interior of the glass tube I0 is now placed in communication with a sourceof vacuum and is suitably evacuated. During this evacuation, the electrode shells [6 are connected with the Opposite poles or the source of current, through the wires 32. This is done to heat the electrode shells I6 and drive oif undesirable gases and impurities.

When the electrode shells 15 are thus connected with the opposite pole of the source of current, of a suitable character, they become highly heated and the tube It] is heated, which aids in baking the coating II. This heating action of the elec-v trode shells I6 is continued for a suitable length of time, indicated by a small piece of paper contacting with the heated tube I l 0 becoming browned or partly charred. When this occurs, the electrode shells l6 are disconnected from the source of current.

After this and when the proper vacuum-is attained' within the tube Ill, Figure 3, the valve 42 is turned to cover the port 40 and hold the vacuum within the tube. Before the tubehas materially cooled, a high frequency coil A is brought into a position for surrounding the lower end of the tube and the lower electrode shell [6, and when the current is turned on, the coil will heat the electrode shell I6 and retainer l8 by induction; This electrode shell and retainer may be heated to a high point and the heat radiating from the same will heat the adjacent portion 51% of the tube, and this portion will be plasticized and drawn inwardly by the action of the vacuum within the tube I 0. This portion 5! By this time, the temperature of the tube I 0 is materially reduced and may be at approximately room temperature, Figure 6. The valve element 50 is now turned to introduce the measured amount of mercury into the port 55 and this mercury drops to the bottom of the tube Hi. This measured amount of mercury is ordinarily a ball of slightly less than 3%" in diameter.

Another high frequency coilA, Figure 7, is now applied to the top of the tube l0 adjacent to the upper electrode shell l6, and this electrode shell is highly heated by the action of the coil and the heat radiating from the shell is and retainer plasticizes the adjacent portion 60 of the tube, which is drawn inwardly by the vacuum within the tube and becomes fused to the retainer l8. This provides a vacuum tight joint and the action may be aided by forming jaws if necessary.

The upper end iii of the tube, Figure 8, is now severed by the blades 62.

Figures 8 and 9 show the complete lamp. The electrode shells iii are arranged within. the opposite ends of the tube In and have their parts or retainers sealed therein to provide vacuumtight joints. The retainers l8 hold the electrode shells in spaced concentric relation to the tube Ill. The contact extensions I! project outwardly beyond'the ends of the tube ill, for engagement with the socket terminals, for supplying current to the lamp when in use.

When the electrodes embodying thecathode shells l6 and shown in Figures 10, 11 and 12, are

will then become fused to the retainer l8 for g forming a. vacuum-tight joint therewith. This action may be aided by the use of forming jaws, if necessary.

The lower end 58 of the tube, Figure 4, is now severed from the tube by knives 59. These knives will not engage the clamp 29 which has a smaller diameter than the retainer l8, as shown in Figure 13.

The valve 41 is now turned to place the tube used, the coil A heats principally the retainer 18, which, in turn, heats and plasticizes the tube I 0.

All other steps of the method remain identical with those shown and described.

It is to be understood that the apparatus herewith shown and described is to be taken as a pre-- ferred embodiment of the same, and that various changes in the shape, size and arrangement of parts may be resorted to, and that changes may be resorted to in the order of the steps of the method, and in the shape, size and arrangement of parts of the cathode units, without departing from the spirit of my invention or the scope of the subJ'oined claims.

Having thus described my invention, what I I claim is:

1. In apparatus for making a cold cathode fluo rescent lamp or the like, a pair of units, each unit comprising a body portion having a chamber'to receive the open end of a glass tube, means carried by the body portion to effect a vacuum tight joint with the glass tube, means for supplying hot air to the chamber of one unit, means for discharging the hot air from the chamber of the other unit, means for connecting the chamber of one unit with the source of vacuum, means for supplying an inert gas to the chamber of one'unit, and means for supplying mercury to the chamber of one unit.

2. An apparatus for making a cold cathode fluorescent lamp or the like, upper and lower units,

' each unit comprising a body portion having a chamber to receive the open end of a glass tube, means to efiect a vacuum-tight joint with the glass tube, means for supplying hot air to the chamber of the lower unit, means to discharge the hot air from the chamber of the upper unit, means for connecting the, chamber oi the lower unit with the source of vacuum, means for supplying an inert gas to the chamber of the upper unit, the body portion of the upper unithaving a well for holding mercury and a recess, a valve element to turn within the recess and having a pocket for receiving mercury, the last named' body portion having a recess below the valve element and 'a port connecting such body portion having a-port leading from the valve element to the chamberof the upper unit, the arrangement being such that the opposite I mercury, and means carried by the body portion electrode within ends of the valve element are sealed with of each unit for Supporting an electrode within the tube.

3. An apparatus -for making a cold cathode fluorescent lamp or the like, comprising a unit hav-- ing a body portion, said body portion having a chamber to receive packing arranged within the chamber to engage with the tube, a cap having'screw-thr aded engagement with the body portion to com ress thethe recess withthe well,

the end of -the glass tube,'.

vices mounted upon the units and extending 'axially through the chambers and including electrodeholding elements which'are arranged ex- 'teriorly of the chambers and units, the arrangement being such that the tube maybe heated and plasticized exteriorly of the units and fused to the electrodes, means'to connect the metallic devices withithe opposite poles of a source of current, and means to evacuate one chamber.

8. In apparatus for making a cold cathode fluorescent lamp or the like irom a tube having open j ends, spaced opposed operating units having chambers which are closed at their outer ends and open at their inner ends to receive the open .ends of the tube, one unit having means to supply mercury into its chamber, packing arranged within the inner ends of the chambers and enpacking, said cap having a cooling jacket, and

mercury and a recess beneath the well, a turning valve within the recess to be turned therein and having a pocket, the body portion having a space beneath the valve element and a port extending between the well and space, the last named port, having a part'leading to the recess, said body por-'- tion also having a port extending from the recess to the chamber, and means to evacuate the tube when its end is held within the chamber.

5. In apparatus for making an electronic device from a tube having an open end, a substan-,

tially vertical meinber provided with a chamber having a lower enlarged portion to receive the open end of the tube, means arranged within the lower enlarged portion to form a vacuum tight joint with the tube, means for supplying mercury into the side of the chamber above the lower enlarged portion, a device mounted upon the memberand extending axially through the cham. her and outwardly of the chamber and member and including a socket at its free end to receive an electrode, said socket holding the electrode in spaced concentric relation within the'tube, the

' arrangement being such that, the tube may be heated and plasticized exteriorly and fusedto the electrode, and means to evacuate the tube andto supply an inner gas to the same.

6. In apparatus for making a cold cathode fluorescent lamp or the like from atube having an open end, a body portion having a-chamber provided with an open end to receive the open end of the tube, means engaging the tube for forming a seal, a metallic member mounted upon the body portion and passing through the closed end of the chamber and extending axially of the chamber and including a' socket disposed outwardly of the chamber and member, saidsocket extending axially of the tube and holding an electrode in the tube, the arrangement being such that the tube may be heated and plasticized exteriorly of the member and fused to the electrode, means to connect the outer end of the metallic member with 'a source of current, and means to evacuate the tube.

Y 7. In apparatus for making a cold cathode fluorescent lamp or the like from a tube havm lits opposite ends open,'spaced operating units having chambers for receiving the open ends of the tube, means for forming seals with. the,

opened end portions of the tubes, metallic dewithin the tube, the arrangement being such that V the tube may be heatedand plasticized exteriorly of the units and fused to the electrodes, and

, means to evacuate one chamber. 7

9. In apparatus for making a cold cathode fluorescent lamp or the like from a tube having opposite open ends, spaced opposed operating units having chambers having outer closed ends and inner open ends to receive the open ends of the tube, means for forming seals with the open .end

portions of the tube, devices mounted upon the units and extending axially of the chambers and including electrode holding units arranged out wardly of the chambers and the first named units,

the arrangement being such that the tube may be heated and plasticized exteriorly of the first named units and fused to the electrodes, and means to evacuate one chamber.

10. In apparatus for making a cold cathode fluorescent lamp from a tube having both ends open and its interior provided with a fluorescent coating, said apparatus comprising spaced operating units having chambers for receiving the open ends of the tube, means for forming vacuum tight joints with such open ends, metallic members carried bythe units and extending axially within the chambers and into the open ends of the tube for holding electrodes within the tube and spaced from each other, means to evacuate one chamber while the adjacent end of the tube is open, and means to connect the metallic members with the opposite poles of a source of current during the evacuation period and while such adjacent end is open so that the electrodes become highly heated for driving on undesirable gasses and impurities.

11. In apparatus for making a cold cathode fluorescent lamp from atube having both ends open and its interior provided with a fluorescent coating, said apparatus comprising spaced operating units having chambers for receiving the open ends of the tube, means for forming vacuum tight joints with such open ends, metallic current during the ate one chamber while the adjacent end of the tube is open, and means to connect the metallic members with the opposite poles of a source of evacuation period and while such adjacent end is Open so that the electrodes become highly heated for driving 01f unde-t sirable gases and impurities.

12. In apparatus for making a cold cathode fluorescent lamp from a tube having both ends open and its interior provided with a fluorescent coating, means for forming vacuum tight joints with such open ends, metallic members carried by the units and extending axially within the chambers and into the open ends of the tube within the chambers for holding electrodes Within the tube and spaced from each other, means to evacuate one chamber while the open ends of the tube are within the chambers, and means to connect the metallic 10 members with the opposite poles of a source of current while the open ends of the tube are within the chambers.

CARL HERZOG.

REFERENCES CITED The following references are of record in the file of this patent:

Number UNITED STATES PATENTS Name Date Marshaus Mar; 9, 1943 Owings Apr. 24, 1945 Harrison et a1 Aug. 10, 1943 Zimber July 2, 1935 McCullough Apr. 27,- 1937 Stewart Sept. 24, 1940 

